The Weldability of Some Arctic-Grade Line-Pipe Steels

8/10/2019 The Weldability of Some Arctic-Grade Line-Pipe Steels

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The W e lda b i l i t y o f Some

Arct ic-Grade L ine-Pipe Steels

Micro-alloy line-pipe steels display good resistance to

HAZ cracking and, with respect to weldab ility, are

generally superior to conven tional line-pipe steels

B Y J . G O R D I N E

ABSTRACT. The we ldab i l i t ies o f n ine

Arc t ic -g rade s tee ls were de te rm in ed

and compared to t he we ldab i l i t y o f a

convent iona l X65 l ine -p ipe s tee l . Two

aspec ts o f we ld ing were examined: t he

s u s c e p t i b i l i t y t o h y d r o g e n - i n d u c e d

heat -a f f ec ted zone (HAZ) c rack ing

and the HAZ Charpy toughness p rop

erties.

I t was shown that the major i ty of the

Arc t ic -g rade s tee ls exh ib i t ed be t te r

HAZ cracking res is tance than the

convent ional X65 steel . I t was a lso

conf i rmed tha t t he convent iona l ca r

bon -equ iva len t f o rmu la is no t va l id f o r

the new h igh-s t reng th low-a l loy s tee ls

and that the

Ito-Bessyo

rel at io n is a

more appropr iate measure to use.

The HAZ toughness measurements

made on G leeb le s imu la ted spec imens

show ed a w i de var ia t ion in behav io r

of the d i f fer ent s teels . Al l sh ow ed

severe loss in toughness in the 1300 C

(2370 F) peak tempera tu re cond i t ion .

Some steels also showed severe loss in

toughness in the 700 C (1290 F) peak

t e m p e r a t u r e c o n d i t i o n .

I n t r o d u c t i o n

Recent o i l and gas d iscover ies in

nor thern Canada have resu l t ed in

several proposals for the const ruct ion

of p ipel ines to t ranspor t these re

sources to the southern market areas.

The p roper t y requ i rements f o r t he

pipel ine steels that wi l l be used to

bui ld these pipel ines are very s t r ingent

and cannot be met by t he conven

t ional types of l ine-pipe steels .

Because o f t he Arc t ic env i ronment ,

very h igh demands have been set on

both st rength and toughness. For

exam ple, the latest Canadian Arct ic

Gas Pipel ine proposal speci f ies a

m i n i

mum yie ld s t rength of 70 ks i (482 MPa)

wi th a Charpy V-n o tch toughness

crit er i on of 30 f t - l b (40 J) at desig n

tem pe ra tur es of 25 C (15 F) or 5 C

(4-25 F) in the case of pipe of 0.72 in.

(18 mm) wal l th ickness.

To meet these di f f icu l t speci f ica

t i ons ,

new s tee l compos i t ions have

been deve lope d and a num ber o f

these so-cal led Arct ic-grade steels are

no w ava i lab le . W h i l e con s iderab le

e f fo r t has gone in to de ve lo p ing the

requ i red mechan ica l p roper t ies in

these new steels , much less at tent ion

has been g iven to the i r we l d in g behav

ior . I t was the purpose of the work

descr ibed in th is paper to examine th is

aspect.

A number o f Arc t ic -g rade l ine -p ipe

s tee ls were purchased, and we ldab i l i t y

tes t s were conduc ted upon them. The

two aspec ts o f we ldab i l i t y se lec ted fo r

examina t ion were :

1.

Suscept ib i l i t y t o HAZ c rack ing .

2.

HAZ toughness character is t ics.

Both aspects w i l l p lay a ma jor ro le in

the u l t imate select ion of s teels for use

in any Arc t ic -p ipe l ine p ro jec t . Bo th

character is t ics are a lso very much a

funct ion of the steel , i tse l f , rather than

of t he we ld ing consumab les used .

HAZ co ld c rack ing is a p rob lem

of ten encounte red in t he f ie ld we ld ing

o f convent iona l l ine -p ipe s tee ls and is

l ike ly to be an even more ser ious

Paper presented at the 58th AWS Annual

Meeting held in Philadelphia, Pennsylvania,

during April 25-29,

1977.

CORDINE is

Research

Scientist, Welding

Section, P hysical Metallurgy Research Lab

oratories, CAN MET, Department of Energy,

Mines and Resources, Ottawa, Canada.

prob lem in t he Arc t ic p ipe l ine p r o j

ects.

Due to t he h igher opera t ing p res

sures,

p ipe wal l th icknesses are

greater, and this wil l result in faster

cool ing rates in the HAZ. Thus, the r isk

o f deve lop ing hard c rack -suscept ib le

microst ructures in the HAZ is much

greater . In addi t ion, the greater wal l

th icknesses wi l l mean that the external

s t ress imposed on the weld dur ing the

lay ing of the p ipe wi l l be greater , and

this wil l also increase the r isk of crack

ing.

The ma in tenance o f adequate

toughness proper t ies in the HAZ is

l ike ly to be a ser ious prob lem in the

we ld ing o f t hese Arc t ic -g rade l ine -

pipe steels . The imp rov ed toug hne ss in

these steels is largely a result of a

f i ne

gra ined m ic ros t ruc tu re p roduced by

care fu l ly con t ro l led ro l l ing t echn iques .

I t can be assumed that weld ing wi l l

a l ter th is carefu l ly regulated micro-

s t ruc tu re and tha t accompany ing these

mic ros t ruc tu ra l changes wi l l be

changes in toughness. The extent to

wh ich the toughness is chang ed in t he

HA Z is no t k no wn . It is c lear , how ever ,

that most Arct ic speci f icat ions wi l l

r equ i re m in imum toughness leve ls in

the HAZ.

Ma t e r i a l s

A general descr ipt ion of the 10 l ine-

pipe steels in the evaluat ion program

is g iven in Table 1. The che mic al

compos i t ions and some representa t ive

mechanical proper t ies are g iven in

Tables 2 and 3.

Al l p ipes were purchased in the

form of a p ipe le ngth a nd al l except

one (p ipe A) were made to de f ined

API spec i f i ca t ions us ing norma l com

merc ia l pract ices. The steels l is ted

W E L D I N G R E S EA R C H S U P P L E M E N T I

201-s


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represent producers f rom Canada,

Japan and West Germany. Al l , except

p ipe F , were con s idered cand ida te

mater ia ls f o r Arc t ic p ipe l ine app l ica

t ions .

The l ine-pipe steels in the program

can be separa ted in to t he fo l l ow ing

three categor ies.

1. C o n v e n t i o n a l l i n e - p ip e s t e e l -

s tee l F ( inc lud ed fo r com para t ive

purposes) .

2.

Co n t r o l l e d r o l l e d m ic r o - a l l o y

l ine -pip e s teels-s teels J, M , N, P, R and

Z.

3 . Q u e n c h e d a n d t e m p e r e d s t e e l s -

steels T and S.

Table

1General

Description of Line Pipes

Pipe

A

F

I

M

N

P

R

S

T

Z

1 in. =

Size, i n . ' " '

( O . D .

X wa l l

th ickness)

30 x

0.375

26 x

0.518

48 X 0.562

42 X 0.380

42 X 0.420

48 X 0.720

48 X 0.720

48 X 1.250

48 X 1.250

42 x 0.540

25.4 mm

API

spec i f i ca t ion

E x pe r i m en t a l

5LX-X65

5LX-X65

5LX-X70

5LX-X65

5LX-X70

5LX-X70

5LX-X65

5LX-X65

5LX-X70

Processing

As-rolled and aged 1 h at 700 C (1300 F)

Controlled-rolled

Controlled-rolled

Controlled-rolled; spiral weld

Controlled-rolled

Controlled-rolled

Controlled-rolled

Quenched and tempered

Quenched and tempered

Controlled-rolled; spiral weld

E x p e r i m e n t a l P r o c e d u r e s

Assessment of Cold Cracking

Susceptibility

Two test methods were used to

d e t e r m in e s u s c e p t i b i l i t y t o h y d r o g e n -

induce d HA Z c rack ing . They were :

1. Co nt ro l le d Therma l Sever it y

(CTS) test ing.

2.

Implant test ing.

Both a re s tandard we ldab i l i t y t es t s

used to de te rm ine the suscept ib i l i t y o f

a s teel to HAZ cold cracking, and fu l l

descr ipt ions are avai lable in the l i tera

tu re .

1

'

2

The tes t we ld ing cond i t ions se lec ted

for both tests were based on those

used fo r manua l g i r t h we ld ing in p ipe

l ines ."

They are summar ized in Table 4.

The energy inputs used were s l ight ly

higher than are normal ly used in g ir th

w e l d i n g , but this was necessary in

order t o p roduce su i t ab le t es t we lds .

In the CTS test, all test welds were

depos i t ed a t t he energy inpu t l i s t ed in

Tab le 4 . A f te r t he recommended 48 h

ho ld ing t ime a t t he tes t t empera tu re ,

t hey were sec t ioned and examined fo r

cracking us ing the wet f luorescent

magnet ic par t ic le process. The test

sever i ty was var ied by lower ing the

test temperature. This was ac

compl ished by conduc t ing the tes t s in

a co ld room in wh ic h the tem pera tu re

cou ld be accura te ly con t ro l led over a

tempera tu re range f rom room temper

a tu re down to -40 C ( -40 F) .

The imp lan t t es t ing p rocedures used

were iden t ica l t o t hose descr ibed by

Sawh i l l . -

I n h is t echn ique the s ing le -

n o t c h e d im p la n t Test bar , as proposed

by Gran jon , i s rep laced wi th a he l ica l

n o t c h . This has the advantage that the

no tch wi l l necessar i ly pass thr ou gh th e

most crack-sensi t ive region of the

HAZ . W i t h G r a n jo n ' s t e c h n iq u e , c a r e

fu l at tent ion must be g iven to ensure

that the notch is accura te ly loca ted in

the cr i t ica l region of the HAZ.

The imp lan t t es t we ld was depos i t ed

manua l ly w i t h L inco ln HYP.E7010

elect rod es at a cons tant energy inp ut .

Two m inu tes a f t e r comple t ion o f t he

test w e l d , the sur face of the assembly

was inver ted in wate r and coo led fo r 4

m i n . The test assembly was then

removed f rom the water and loaded in

a mod i f ied c reep mach ine exac t ly 10

min a f t e r comple t ion o f t he imp lan t

testw e l d . Approx imate ly 12 spec imens

f rom each steel were tested in order to

produ ce a s tress vs. t im e- to - rup tu re

curve f rom wh ich cou ld be de te r

mined the cr i t ica l s t ress value for the

steel.

HAZ Toughness Testing

HAZ toughness was assessed by

means of the Charpy impact test , us ing

-size

specim ens. Ear l ier w ork on

submerged-arc seam we ld s sho we d

tha t ex t reme var ia t ions were ob ta ined

in the Charpy impact values in the

HAZ due to t he d i f f i cu l t y o f con t ro l

l ing the prec ise locat ion of the notch

in t he HAZ. To overcome th is p rob lem

the RPI Gleeble was used to s imulate

speci f ic locat ions in the HAZ of real

we lds , and the Charpy impac t va lues

o f t hese s imu la ted spec imens were

d e t e r m in e d .

The thermal cyc les used in the HAZ

s imu la t ions were based on ac tua l

measured thermal cyc les f rom the root

pass of a manual gir th w e l d .

4

The

therma l cyc les exper ienced in t he HAZ

dur ing the root pass of a manual g ir th

weld are ext remely severe in terms of

the rapid heat ing and cool ing rates.

The actual measured thermal cyc les

are sh ow n in Fig. 1.

Th e G le e b le e q u ip m e n t c o u ld n o t

accura te ly reproduce these hea t ing

and coo l ing ra tes . There fo re , a d e c i

sion was made to use the most rapid

therma l cyc les t ha t t he G leeb le cou ld

produce. These thermal cyc les are

sho wn in Fig. 2. The co ol in g rate was

enhanced by he l ium gas coo l ing . The

spec imens used were

2

/3-size

Charpy

bars 3 in. (76 mm) long and with no

n o t c h . A f t e r t herma l cy c l ing , t he spec

imens were no tched a t t he cen te r

wh e r e t h e c o n t r o l t h e r m o c o u p le wa s

at tached and then cut to proper

l e n g t h .

A l l Charpy spec imens were

or ien ted such tha t t he long d i rec t ion

was perpend icu la r t o t he o r ig ina l

ro l l ing d i rec t ion o f t he p la te .

Co m p le t e Ch a r p y V - n o t c h t r a n s i ti o n

curves were ob ta ined fo r each therma l

cyc le cond i t ion . Therma l cyc les hav ing

peak tem pera tures of 700, 900, 1100

and 1300 C (1290, 1650, 2010 and 2370

F) we re used. Three specim ens we re

tested per temperature, and usual ly

tests were made at seven di f ferent

temperatures to establ ish the

t ran

si t ion curves.

Exper imenta l Resul ts

Cold Cracking Tests

The results of the CTS tests on the

d i f f e ren t l ine -p ipe s tee ls a re summa

r ized in Tab le 5 . Da ta were ob ta ined

for eight of the ten steels in the

p r o g r a m .

Plate th icknesses used were

dete rm ined by the wa l l t h ickness o f

the p ipe and ranged f rom 0.375 to

0.720 in. (9.5 to 18.3 mm) with the

c o r r e s p o n d in g t h e r m a l s e v e r i t y n u m

ber vary ing f rom 5 to 7. Also s ho wn in

Tab le 5 a re the ma x im um HAZ

h a r d

ness values recorded. Selected test

welds f rom the CTS tests were

sec t ioned and po l ishe d , and hardness

t raverses were made across the weld

and H AZ u sing a Vickers hardness

tester with a 10 kg (22 lb) l oad . In most

cases, the maxi mu m H AZ hardness

cor responded to t he reg ion o f t he HAZ

through wh ich the c rack t raversed .

A t yp ica l c racked sec t ion th rough a

CTS test weld is shown in Fig. 3. This

par t icu la r examp le is t he c onv ent i ona l

l i n e - p ip e

steelsteel Fwhich

e x h i b

ited a large crack that ran en t ire ly

th rough the coarse-gra ined reg ion o f

t he HA Z a t a t est t empera tu re o f - 1 6 C

(

+

3

F).

I n some spec imens , t he c rack ing

fo l lo we d a s tep- l i ke pa th ru nn i ng

between e longated inc lus ions ; an

exam ple is sh ow n in Fig. 4.

I n genera l , t he amount o f c rack ing

observed in all steels in the CTS tests

202-s | JULY 197 7


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T ab l e 2 M anu f ac t u re r s ' A na l y s es o f L i ne -P i pe S t ee l Chem i c a l Com pos i t i ons , %

Line Pipe

A

F

M

N

P

R

S

T

Z

c

0.04

0.16

0.11

0.06

0.07

0.10

0.10

0.10

0.05

0.05

M n

0.44

1.25

1.28

1.65

1.38

1.47

1.48

1.30

0.67

1.94

P

0.010

0.008

0.014

0.012

0.010

0.017

0.014

0.008

0.015

0.007

S

0.015

0.009

0.008

0.014

0.009

0.004

0.002

0.003

0.003

0.011

Al

_

-

0.033

-

0.050

0.039

0.033

0.034

0.035

-

N b

0.04

0.047

0.04

0.054

0.140

0.04

0.05

0.03

0.04

0.060

Si

0.27

0.35

0.25

0.04

0.27

0.25

0.30

0.28

C u

1.22

0.19

0.28

0.31

0.93

N i

0.91

-

-

0.19

-

0.28

0.32

0.45

0.96

-

Cr

0.67

-

-

0.09

-

-

-

-

0.29

M o

0.20

-

-

0.24

-

-

-

0.08

0.30

0.49

Sn

-

-

0.014

-

-

-

-

-

V

-

0.06

-

0.09

0.10

-

-

-

N

-

0.005

-

-

-

-

-

-

T ab l e

3Representative

M ec h an i c a l P rope r t i es o f L i ne -P i pe S t ee l s " "

Cha rpy abs o rbed ene rgy

58 f t - l b at - 2 9 C ( -2 0 F ) -2 / 3 s iz e

42 f t - l b , 97% shear a t -4 C ( + 25 F) -2 /3 s i ze

38 f t - l b , 100% shear a t -29 C ( -20

F) full

s ize

59 f t - l b a t -2 9 C (-20

FJ-2/3

s ize

66 f t - lb , 88% shear at - 4 C ( + 25 F)2/3 s ize

40 f t - l b , 90% shear a t -6 0 C ( -7 6

F)full

s ize

127 f t - l b , 100% shear a t -60 C ( -76

F)full

s ize

217 f t - l b , 100% shear a t -2 9 C ( -2 0

F)full

s ize

187 f t - l b , a t - 29 C ( - 20

F) full

s ize

76 f t - l b , 95% shear at -2 9 C ( -2 0

F)full

s ize

Tab le

4 -We ld ing

Cond i t i ons Us ed i n

Cold Crack ing Weldab i l i t y Tes ts

Steel

A

F

I

M

N

P

R

S

T

Z

ksi X 6.89 =

Yield

stress,

ksi

84.0

67.2

66.7

72.3

67.0

77.2

74.7

72.1

75.1

73.0

MPa; ft-lb X

U l t i m a t e

tens i le

stress,

ksi

87.0

91.8

84.8

91.3

81.1

95.3

88.5

94.0

90.8

91.8

1.356 = Joules

w a s s m a l l a n d w o u l d i n d i c a t e a g o o d

r e s i s t a n c e t o H A Z c r a c k i n g . I n m a n y

s p e c i m e n s e x a m i n e d , s m a l l c r a c k s

w e r e o b s e r v e d i n t h e w e l d m e t a l

r a t h e r t h a n i n t h e H A Z , i n d i c a t i n g t h a t

i n m a n y o f t h e s te e l s h y d r o g e n

c r a c k i n g is m o r e l i k e l y t o o c c u r i n t h e

w e l d m e t a l .

I m p l a n t t e s ts w e r e m a d e o n a l l t e n

s t ee l s i n c l u d e d i n t h e e v a l u a t i o n

p r o g r a m .

In

t h e i m p l a n t te s t a r e l a t i o n

s h i p o f a p p l i e d s t re s s v e r s u s t i m e - t o -

f a i l u r e is e s t a b l i s h e d . F r o m t h i s r e l a

t i o n s h i p a s tr e s s l e v e l m a y b e d e t e r -

Test

CTS

Implant

Electrode

L inco ln

HYP.E 7010

L inco ln

HYP.E7010

Energy

i npu t

780 J /mm

(20,000 J/ in.)

1560 J /mm

(40,000 J/ in.)

m i n e d a t w h i c h a s p e c i m e n h a s a 5 0 %

p r o b a b i l i t y o f f a i l i n g in t h e i m p l a n t

t es t . T h i s st r es s i s d e f i n ed as t he C r i t

i ca l 5 t ress (CS) an d can be us ed as a

f u n d a m e n t a l m e a s u r e o f t h e r e s i s t a n c e

o f a s t e e l t o h y d r o g e n - i n d u c e d c o l d

c r a c k i n g . A h i g h C S v a l u e i n d i c a t e s t h e

s t e e l w i l l h a v e a h i g h r e s i s t a n c e t o

H A Z c o l d c r a c k i n g i n w e l d i n g ;

c o n

v e r s e l y , a l o w C S v a l u e i n d i c a t e s a l o w

t o l e r a n c e t o h y d r o g e n d u r i n g

w e l d

i n g .

I n F ig . 5 , t y p i c a l s t r e s s / t i m e c u r v e s

o b t a i n e d f r o m t h e i m p l a n t t e s t a r e

1

I T

J

L

J

I I I

Fig.7The thermal cycles experienced in the root pass HAZ for the lowest practical heat input c ondition used in manu al pipeline

arc welding

W E L D I N G R E S E A R C H S U P P L E M E N T I 2 0 3 -s


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i i i i r

i i i i

i r

r

- 2 3 7 0 *F (1300 *C) PEAK

S I MUL A TE D

TrCRMAL

CYCLES

T I M E (SEC)

Fig.2The best simulation of the actual manual pipeline weld thermal cycles obtainable on the Gleeble

Table 5Controlled Thermal Severity Test Results for Line

Steel

A

F

J

M

N

P

R

S

T

Z

T he rm a l

severi ty

n u m b e r

5

6

6

5

5

7

7

6

6

6

M ax . HA Z

Vickers

hardness

318

435

352

274

255

442

422

429

352

355

Pipe Steels

Tes t t empera ture a t

wh i c h c rac k i ng f i r s t

o c c u r r e d

< - 3 6 C

- 1 6 C

+

21

C

- 2 7 C

- 3 6 C

- 1 7 C

- 1 7 C

+ 21 C

< 0 C

< 0 C

(-32 F)

(

+ 3 F)

(

+

70

F)

( -16 F)

( 32 F)

(

+

2

F)

(

+

2

F)

( + 70 F)

(+ 32 F)

(

+ 32 F)

shown for three selected steels in the

eva lua t ion p rogram . The da ta in F ig . 5

show the two ex t remes o f behav io r .

Steel R ex hib its a CS val ue of 47.0 ksi

(324 MPa) , whereas steel M has a

much higher value of 87 ks i (600 MPa) .

A lso shown fo r compar ison is t he

s t ress / t ime curve fo r t he convent iona l

C-Mn X 65 steel, i .e. , steel F.

A summ ary o f t he en t i r e imp lan t

results for all ten steels is given in

Table 6. The resul ts sh ow a w id e range

in CS values for the ten d i f fe ren t ma te

r ials. All steels tested, except for steels

P and R, sh ow ed CS values h igher than

tha t o f t he con ven t iona l l ine -p ipe

s tee l , steel F.

As in the CTS tests, sect ions were

taken th rough se lec ted f rac tu red im

p lan t t es t spec imens and examined

meta l lograph ica l ly . A t yp ica l example

is sh ow n in Fig. 6 and sh ows the

f racture is a lmos t ent i re ly in th e

coarse-gra ined reg ion o f t he HAZ. Th is

was not a lways the case, and some

steels ( | , M and S) behaved in an

anomalous manner and f rac tu red ou t

s ide of the HAZ. This occurred only at

the h igher appl ied st resses.

Hardness measurements us ing the

Vickers Hardness Tester were made

across selected implant test spec

imens , and the max imu m va lues

recorded in t he HAZ are shown in

Table 6.

HAZ Toughness

The var ia t ion in t he toug hness

across the HAZ of the l ine-pipe steels

was de te rm ined by tes t ing s imu la ted

HAZ 's p roduced in t he G leeb le . Four

l o c a t i o n s w i t h i n t h e HAZ we r e s e

lec ted fo r s imu la t ion , and a su f f i c ien t

number o f spec imens were s imu la ted

such tha t comple te Charpy impac t

t rans i t ion curves cou ld be de te rm ined

fo r t hese four loca t ions . The four loca

t ions se lec ted fo r s imu la t ing were

those regions that heated to peak

temperatures of 700, 900, 1100 and

Fig. 3Example of HAZ cracking in

CTS

test

specimen of line-pipe F.

X6

1300 C (1290,1650, 2010, 2370 F) during

w e l d i n g .

Only six of the ten steels in the

eva lua t ion p rogram were tes ted in t h is

manner . The vo lume o f da ta genera ted

f rom th is t ype o f exper imenta l work

was large and is merely summar ized

here in an a t t empt t o show genera l

t rends in behavior .

F igure 7 shows the C harpy impa c t

t rans i t ion curves fo r t he s imu la ted

204-s JULY 1977


5/10

HAZ o f conve nt ion a l s tee l F. A s ign i f i

cant loss in Charpy impact toughness

can be seen fo r th e 1300, 900 an d 700 C

(2370,

1650 and 1290 F) peak tempera

ture condi t ions. Only the 1100 C (2010

F) co nd i t io n ma in ta ins impac t t oug h

ness equivalent to the parent s teel .

The m ic ros t ruc tu res tha t cor respond

to the four peak tempera tu re cond i

t ions are show n in Fig. 8. No s ign i f i

can t m ic ros t ruc tu re changes cou ld be

observed in the 700 C (1290 F) peak

tempera tu re cond i t ion tha t cou ld ex

plain the drast ic loss in toughness

shown in Fig. 7. Only the 1300 C (2370

F) co nd i t ion e xh ib i t ed a m ic ros t ruc

tu re t ha t cor re la ted w i th t he tough

ness levels obta ined.

Steels P and M exh ib i te d a s imi lar

type of behavior wi th severe losses in

toughne ss prope r t ies in both th e 700 C

(1290 F) and 1300 C (2370 F) peak

tempera tu re cond i t ions .

The pat tern of behavior observed in

the con ven t iona l s tee l was no t com

mon to all the steels tested. Steel A

show ed a d i f f e ren t behav io r as show n

in Fig. 9.

In

this case only the 1300 C

(2370 F) peak tempera tu re cond i t ion

caused degrad at ion o f impac t t oug h

ness. The o ther peak temp era tu re

c o n d i t i o n s s h o we d im p a c t t o u g h n e s s

values equ ivale nt to , or bet ter than,

t he paren t s tee l . The m ic ros t ruc tu res

cor respond ing to t he four peak

t e m

perature condi t ions for s teel A are

sho wn in Fig. 10. Steel N show ed a

simi lar type of behavior to that of s teel

A.

The f inal pat tern of behavior was

tha t observed fo r t he quenched-

an d- te mp ere d steel S. The resul ts are

sho wn in Fig. 11.

In

this case, the 700 C

(1290 F) peak tempera tu re cond i t ion

has impact toughness levels c lose to

the parent steel. The 900, 1100 and

1300 C (1650, 2010 and 2370 F) thermal

cyc les , however , p roduced a s ign i f i

cant drop in toughness proper t ies. The

d i s t i n c t i o n b e t we e n t h e b e h a v io r o f

this steel and the other steels is that, in

re lat ive terms, the loss in toughness is

muc h g rea te r . The m ic ros t ruc tu res cor

respond ing to t he four peak tempera

ture con di t i on s in s teel S are sh ow n in

Fig. 12;

t hey cor re la te we l l w i t h t he

observed toughness p roper t ies .

An overal l summary of the resul ts

for the six steels tested is given in

Table 7. Here the data have been

presented in terms of Charpy absorbed

energy values at 29 C (20 F) and 62

C ( -80 F) for the four peak tempera

ture condi t ions and also for the parent

meta l .

Discussion

The we ldab i l i t y t es t s conduc ted on

the n ine Arc t ic -g rade l ine -p ipe s tee ls

to de te rm ine the i r suscept ib i l i t ies t o

h y d r o g e n - i n d u c e d HAZ c r a c k in g c o n -

AyrS'^^kS^MMfmrn

i

mm

mr--AAM

r..

Fig.4Example of HAZ crack in line-pipe M in CTS test made at -37 C(-35 F) showing

association of crack with inclusions. X100

^r - 6 0 0

1 0 1 0 0

T I M E T O R U P T U R E . MIN

Fig.

5Implant

test results for steels M, F and R

Table

6 -

Stee

A

F

J

M

N

P

R

S

T

Z

Summary of Implant Test Resu

Carbon

Equiva lent

Conv en t i ona l I t o

.43

.37

.34

.43

.30

.40

.41

.36

.41

.47

I ts on Line-Pipe Steels

-Bessyo

.19

.23

.19

.18

.14

.21

.21

.19

.18

.18

Lower

c r i t i ca l

stress,

ksi

82.0 (565 MPa)

61.2 (421 MPa)

87.0 (600 MPa)

87.0 (600 MPa)

86.6 (595 MPa)

59.2 (407 MPa)

47.0 (324 MPa)

71.0 (490 MPa)

76.0 (524 MPa)

65.0 (448 MPa)

M a x i m u m

HA Z

Vickers

hardness

303

442

326

274

294

422

360

360

391

336

f i rmed tha t t he ma jo r i t y had lower

levels of suscept ib i l i t y than the one

convent iona l l ine -p ipe s tee l t ha t was

also tested. On ly s teels P and R

show ed a g rea te r suscept ib i l i t y t o co ld

c rack ing than the convent iona l s tee l .

Of the two test methods used to

de te rm ine the suscept ib i l i t y t o co ld

c rack ing ,

the imp lan t t es t was foun d to

give a mo re sensi t ive m easure o f

c rack ing suscept ib i l i t y , and more re

l iance was placed upon these resul ts

than those f rom the CTS test . The CTS

resul ts shown in Table 5 indicate l i t t le

rea l d i f f e rence be tween the c rack ing

suscept ib i l i t ies of the ten steels tested.

On ly s tee ls A, M and N showed a

c rack ing tenden cy low er t han the

conv ent ion a l l in e -p ip e s tee l . They a lso

showed much lower HAZ hardness

levels . The remaining steels showed

per formances equal to or , in some

cases , worse than th e con ven t iona l

steel.

W E L D I N G R E S E A R C H S U P P L E M E N T I 2 0 5-s


6/10

-

Fig.6Cross

section through fractured implant specimen of line-pipe R.X5 (reduced 14 on

reproduction)

T E S T T E M P E R A T U R E . C

5 0 0 5 0

T^ T^

1^

8 0

tn

4 0

H

T E M P E R A T U R E

Fig.7Charpy V-notchimpact properties of C leeble-simulated heat-affected zones

in line-pipe F(

2

A-size specimens)

The CTS test is better suited to

th icker -gauge mater ia ls where the tes t

sever i t y can be con t ro l led by vary ing

the spec imen th ickness . I n t h is work ,

the test sever i ty was increased by

lower ing the tes t t empera tu re . Th is

in t rod uce d exper im enta l d i f f i cu l t ies

wh ich reduced the accuracy o f t he

test . In fact , considerable scat ter in

resu l t s was ob ta ined .

On the posi t ive s ide, the CTS does

represent a real res t ra ined we ld co nd i

t ion s imi la r to that pro du ce d in a

c i r c u m f e r e n t i a l g i r t h w e l d . The jo in t

con f igura t ion is , o f course , comp le te ly

d i f f e ren t , be in g a f i l le t we ld ra ther

than the single-V bu t t jo in t in a

c i r c u m f e r e n t i a l p i p e w e l d . Ho we v e r ,

a t t empts t o use a we lda b i l i t y t es t w i t h

a bu t t con f igu ra t io n , such as the

Tekk en test and others , we re no t

successfu l s ince cracking occurred

almost exc lus ively in the weld metal

rather than the HAZ.

I t was concluded that these tests

were eva lua t ing we ld meta l c rack ing

suscept ib i l i t y ra ther t han HAZ c rack

ing ; t h e y we r e , t h e r e f o r e , d i s c o n t i n

ued . In the CTS test , crack ing could be

more read i ly p roduced in t he HAZ. I n

most s teels tested, however , crack ing

a lso occur re d in t he w e ld me ta l , and i t

mus t be con c lu de d tha t in many o f

t hese mater ia ls hydro gen - ind uce d

crac king of the we ld m etal is l ike ly to

be a more ser ious p rob le m than

crack ing in t he HAZ.

The imp lan t test gave a mu ch bet te r

d i f f e r e n t i a t i o n b e t we e n t h e c r a c k in g

suscept ib i l i t ies o f t he d i f f e ren t l ine -

pipe steels. The results in Table 6

sho w a w id e range in the CS values

for the d i f ferent s teels . This , in tu rn ,

w il l m ean a w id e range in the re lat ive

co ld -c rack ing suscept ib i l i t ies f o r t he

dif ferent steels. Steels A, M and N

showed h igh res is tance to co ld c rack

ing as ev id enc ed by their h ig h CS

values. This is in go od a greem ent w i th

the CTS resul ts obta ined on these

three steels . Steel J a lso showed a h igh

CS va lue bu t d id no t per fo rm as we l l in

the CTS tests. Of the remaining steels

(except for P and R) , a l l show ed high er

CS va lues than the con ven t iona l l in e -

pip e steel F. Steels P and R had CS

va lues be low tha t o f t he convent iona l

steel.

Also sho wn in Tab le 6 a re t he carbo n

equ iva len ts (CE. ) f o r t he ten d i f f e ren t

s tee ls . The carbon equ iva len t i s com

mo nly used as an indic ato r of the

tend enc y of a s teel to hard en ing in th e

HAZ a n d s u s c e p t i b i l i t y t o h y d r o g e n -

induced c rack ing . Mos t p ipe l ine spec i

f i ca t ions impose upper l im i t s upon the

C E .

va lues of the l ine-pipe steels . The

carbon equ iva len t f o rmu la used in

most p ip el in e spec i f icat ion s is as

f o l l o ws :

M n Cr + M o + V

C E. = C - - -

Ni + Cu

15

Al though th is f o rmu la works very

we l l f o r t h e c o n v e n t i o n a l C / M n l i n e -

pipe steels , i t has been recognized by

many workers that i t is not as appro

pr iate for the newer micro-al loy s teels .

The resul ts in Table 6 co nf i r m th is very

c lear ly . For example, s teels A, M and Z

have h igh CE . va lues as de te rm ine d by

the above fo rmu la and ye t show qu i t e

low HAZ hardnesses and high

resis tances to HAZ cracking. C o n

verse ly , con ven t iona l l ine -p ipe s tee l F

has on e of the low est C E . values an d

yet has h igh HAZ hardness and low

to le rance to HAZ co ld c rack ing .

At tempts have been made to mod i f y

t h e CE . f o r m u la . O n e r e l a t i o n s h ip t h a t

has been repor ted to work mu ch

bet ter for the micro-al loy s teels is the

f o r m u la p r o p o s e d b y Ito and Bessyo/ '

The i r f o rm u la is as f o l low s :

206-sl JULY 1977


7/10

C E . = C + ^ +

M n

30

20

+

Cu

20

-->*-',

Ni Cr M o V

- + + + + 5 B

60 20 15 10

The CE. va lues ob ta ined us ing th is

re lat ionship are a lso l is ted in Table 6.

In

th is case the cor re lat ion of

C E .

value to HAZ hardness and cracking

suscept ib i l i t y is mu ch be t te r a l t houg h

st i l l not per fect . I t would appear that

th e

Ito-Bessyo

f o rmu la is , however , a

bet ter measure of the CE. of the

mic ro-a l loy s teels and is a mo re

reasonab le gu ide to t he we ldab i l i t y o f

the steel.

The results obta ine d for s teels P and

R ind ica te danger in p lac ing too mu ch

re l iance upon the C E . va lues. Both

steels have reasonably low CE. values

and yet show a low res is tance to

hydrogen c rack ing . No c lear exp lana

t ion fo r t h is was de te rm ined . How

ever , both steels have heavi ly banded

mic ros t ruc tu res w i th l o n g , heavi ly

ro l led out inc lus ions. Both factors have

an impor tan t bear ing upon the suscep

t ib i l i t y t o hydrogen c rack ing . Unfo r tu

na te ly , no CE. f o rmu la can take in to

account these factors.

Th e d e t e r m in a t i o n o f HAZ t o u g h

ness of the l ine-pipe steels is a d i f f icu l t

p rob lem due to t he nar row wid th o f

t he HAZ and the w ide var ia t ion in

m ic ros t ruc tu re ac ross i t s w id th . Mos t

Arct ic p ipel ine speci f icat ions st i l l ca l l

f o r m in imum toughness va lues in t he

HAZ and usual ly speci fy the test

p rocedure to be the Charpy impac t

test . The Charpy impact values ob

ta ined when tes t ing the HAZ o f t he

we ld w i l l be a f un c t io n o f t he loc a t ion

o f t he no tch w i th in t he HAZ and,

un fo r tu na te ly , th is is o f t en no t spec i

f ied.

O n e s o lu t i o n t o o b t a in i n g m o r e

mean ing fu l Charpy impac t va lues in

the H AZ is the appro ach used in th is

worknamely

to test

G l e e b l e - s i m u -

lated

HAZ specimens. This a lso has i ts

l imitat ions. I t does not represent the

t rue condi t ion of the HAZ, s ince at

least part of the HAZ is reheated by

subsequent weld passes. Also, the

G leeb le cou ld no t s imu la te exac t ly

the most severe thermal cyc les exper i

enced in the HAZ of the root pass of

the g ir th

w e l d .

This is not as impor tant

as i t w o ul d appear s ince the rem ain ing

we ld passes are de pos i ted us ing h igher

energy inpu ts t ha t wou ld p roduce

s lower HAZ coo l ing ra tes wh ich wo u l d

approx imate those p roduced in t he

Gleeble. The thermal cyc les used

w e r e ,

there fo re , qu i t e represen ta t ive

o f t he overa l l t herma l cyc le cond i t ions

in the HAZ of the g ir th

w e l d .

The resu l t s ob ta ined f rom the

G l e e -

ble-simulated

HAZ spec imens have

conf i rm ed tha t t here is a w i de var ia

t ion in the impact proper t ies across

(A ) A S R O L L E D

7f .

( D ) 1 1 0 0 C (E) 1 3 0 0 C

Fig.8Simulated HAZ microstructures in line-pipe

F.

X250 (reduced 7 on reproduction)

T E S T T E M P E R A T U R E .

- 1 0 0 - 5 0

T E S T T E M P E R A T U R E . F

fig. 9CharpyV-notch

impact properties of

Gleeble simulated

heat-affected zones

in line-pipe A

(

2

A-size

specimens)

W E L D I N G R E S E A R C H S U P P L E M E N T I 2 07 -s


8/10

(A ) AS RECEI V E D

(D)

1100

c

(E ) 1 3 0 0 C

120

6 0

3 0 -

1 0 0

I

T E S T T E M P E R A T U R E , C

5 0

0 50 10 0

AS R OLLED

7 0 0 C

13 00 C

9 0 o.

I

-

3 0

f ig. 10Simulated HAZ microstructuresof

line-pipe

A. X400

(reduced 7

on

repro

duction)

the

HAZ in al l

s tee ls tes te d. Further

m o r e , th e behav io r of each s tee l is

d i f fe ren t .

In

gene ra l

the

steels can

be

separated in to three groups of b e h a v

ior. First

are

those such

as

steels

F, P

a nd

M

wh ich show ed la rge losses

in

toughness in the1300 C (2370 F) and

70 0 C (1290 F) p e a k t e m p e r a t u r e

the rma l cyc le t rea tmen ts .

The

second

group (s tee ls

A

and

N)

o n l y s h o w e d

a

toughness loss in the1300 C (2370F)

p e a k t e m p e r a t u r e c o n d i t i o n w i t h the

rema in ing the rma l cyc les hav ing l i t t l e

e f fec t

or

a c t u a l ly i m p r o v i n g t o u g h

ness. Th et h i r d t y p e of b e h a v i o rwas

tha t dep ic ted bys tee l S; th is sh ow ed a

large loss in toughness for all t h e r m a l

cyc les except

the

700

C

(1290

F)

peak

tempera tu re the rma l cyc le .

Of the

th ree types of b e h a v i o r , the second

t y p e s h o w n bysteels A a nd N is mos t

des irab le .

The exact s ign i f icance

of

hav ing

bands

of

l ow toug hness ma te r ia l

in the

H A Z is notf u l l y u n d e r s t o o d . It canbe

assumed that it w i l l cause an overa l l

l o w e r i n g

of the

duc t i le f rac tu re

resistance

of the HAZ

and , the re fo re ,

s h o u l d bem i n i m i z ed . Al lsteels te sted

showed ve ry low toughness co r re

s p o n d i n g

to

the 1300 C (2370 F) region,

and

it is

un l i ke ly tha t mu ch

can be

d o n e top reve nt th is .It is a very nar row

b a n d w i t h i n theH A Z a n d , p r o v i d e d it

i s su r rounded by ma te r ia l of g o o d

toughness ,

is

p r o b a b l y

not

v e r y h a r m

ful .

For s tee ls tha t deve lop poo r tough

ness in o the r reg ions in the HAZ,

h o w e v e r ,

a

mo re ca re fu l app ra isa l

of

the ove ra l l p rope r t ies

of the HAZ

s h o u l d be m a d e . E x a m i n a t i o n of th e

results inTab le 6show s that severa lof

the steels tested have

low

Cha rpy

impact va lues across most

of

the HAZ .

It

is

un l i ke ly tha t they cou ld mee t

the

m i n i m u m l o w - t e m p e r a t u r e C h a r p y

impac t requ i remen ts for theHA Z tha t

w i l l

be

d e m a n d e d

in the

A rc t i c p ipe

l ine spec i f ica t ions .

C o n c l u s i o n

The pu rpose of t h i s w o r k was to

compare the we ld ing cha rac te r i s t i c s

of

a n u m b e r of so -ca l led A rc t i c -g ra de

l ine -p ip e s tee ls . Tw o aspectsofw e l d a

b i l i t y we re cons ide red . They were

the

suscep t ib i l i t y

to HAZ

hyd rog en c rack -

fig. 11Charpy V-notch impac t p roperties

of Cleeble-sim ulated heat-affected zones

in line-pipe S

(

2

A-size

specimens)

208 -s IJULY1977


9/10

i ng and the va r ia t ion in Cha rpy tough

ness in the HAZ. Both are c r i t ica l

fac to rs tha t w i l l qua l i f y the se lec t ion

of p ipe l ine s tee ls to be used in the

Arc t ic . Th is does not mean that these

two fac to rs a re the on ly we ld ing

cons ide ra t ions to be made . O f e qua l

i m p o r t a n c e w i l l b e t h e d e v e l o p m e n t

o f the requ i red p rope r t ies in the we ld

meta l .

Th is is , howe ve r , m ore a fun c

t ion o f the we ld ing p rocess and the

we ld ing consumab les used than o f the

s tee l be ing we lded , and was the re fo re

no t cons ide red in th is wo rk .

The resu l ts have shown that there is

a wi de var ia t io n in beh av ior fo r th e

d i f fe rent s tee ls tes ted desp i te the i r

s im i la r compos i t ions and m ic ros t ruc

tu res. In gene ra l , i t was co nc lu de d

tha t the we ldab i l i t y cha rac te r i s t i c s o f

the A rc t i c -g rade s tee ls we re be t te r

than those o f the conven t iona l s tee l .

In the HAZ c rack ing suscep t ib i l i t y

tes ts i t was shown that a l l bu t two

steels

testedsteels

P and

Rhad

a

bet ter res is tance to HAZ hydrogen

c rack ing than the conven t iona l s tee l .

The poor c rack ing res is tance o f s tee ls

P and R was tho ug ht t o be re la ted to

the i r heav i l y banded m ic ros t ruc tu re .

The modi f ied implant tes t used in

th is work was found to be a sens i t ive

tes t fo r de te rm in ing suscep t ib i l i t y to

h y d r o g e n - i n d u c e d H A Z c r a c k i n g . T h e

CTS tes t gave much less rep rod uc ib le

resu l ts and was not sens i t ive enough

to d i f fe rent ia te between the s tee ls

tes ted.

Examinat ion o f the ten s tee ls on the

basis o f the i r CE . va lues co nf i rm ed

tha t the conven t iona l CE. quo ted in

most spec i f ica t ions is not va l id fo r

these new h igh -s t reng th low -a l lo y

steels. The Ito-Bessyo re la t ionsh ip was

found to co r re la te qu i te we l l w i th the

implant test results and is a more

appropr ia te formula to use for the

micro-a l loy s tee ls .

In the s tudy o f the HAZ toughness

us ing Gleeble-simulated spec imens, i t

was shown tha t a w i de va r ia t ion in

toughness wi l l ex is t across the HAZ

and that the ex tent o f th is var ia t ion is

d i f fe ren t in each s tee l , The o n ly

common fac tor to a l l s tee ls was the

severe loss of toughness that is

produced in those reg ions o f the HAZ

tha t a re hea ted th rough a we ld

the rma l cyc le hav ing a peak temp era

ture of 1300 C (2370 F).

In som e steels (F, M , and P) a s imila r

loss in toughness occurs in the 700 C

(1290 F) peak temperature reg ions o f

the HAZ, bu t w i th no obse rvab le

change in m ic ros t ruc tu re . In the one

q u e n c h e d - a n d - t e m p e r e d s t e e l t e s t e d ,

the Charpy toughness was reduced

across the ent i r e HA Z except fo r t he

700 C (1290 F) region.

It mus t be conc luded tha t a ca re fu l

app raisal o f the low - tem per a tu r e HAZ

toughness shou ld be made be fo re

( A ) A S R O L L E D

E atvam^a i

J l

Z S&A-\

mmMmmm

( B ) 7 0 0 C

J l

(C ) 9 0 0 C

( D ) 1 1 0 0

U

C

( E ) 1 3 0 0 C

Fig.

12 Simulated

HAZ microstructures of line-pipe S.

X250

(reduced 15 on reproduc

tion)

Table7Charpy Absorbed Energy Values for Gleeble-Simulated Heat-Affected Zones of

Line-Pipe Steels-2/3-Size Specimens Tested at -29 and -62 C (-20 and -80 F)

Peak temperature condition

Steel

A

F

M

N

P

S

A

F

M

N

P

S

As-

ro l l ed

57

22

60

50

35

192

35

-

22

-

25

185

700 C 900 C

(1290 F) (1650 F)

- A b s o r b e d e n e r g y a t 29 C (

48 64

8 14

10 95

44 78

12 23

186 120

- A b s o r b e d e n e r g y a t - 6 2 C (

34 58

4 8

4 65

14 63

7 13

176 100

- 2 0

- 8 0

F)

F)

1100 c

(2010 F)

50

27

72

35

14

68

-

36

20

15

18

7

42

1300 C

(2370 F)

26

11

6

1

8

50

16

11

6

1

8

50

se lec t ing a l ine -p ip e s tee l fo r app l ica

t ion in an A rc t i c env i ronmen t . The

resu l ts o f th is work show that the wide

va r ia t ion in toughness p rope r t ies tha t

can occur across the HAZ are not

p red ic tab le on the bas is o f compos i

t ion o r m ic ros t ruc tu re . The G leeb le

approach used in th is work is a usefu l

W E L D I N G R E S E AR C H S U P P L E M E N T | 2 09 -s


10/10

t e c h n iq u e t o o b t a in i n g a f u l l e r u n d e r

s tand ing o f t he behav io r o f t he HAZ

on we ld ing these mater ia ls .

Acknowledgments

Thanks are expressed to Dr. R. | .

Cooke fo r h is s ign i f i can t c on t r ib u t io n

to t h is work . Apprec ia t ion is a lso

expressed to M. Letts for his assistance

in the exper imental work. Final ly ,

thanks are expressed to Dr . K. Winter -

ton for in terest and input to the

wo r k .

References

1. Campbell, W. P., "Experiences with

HAZ Cold Cracking Tests on a C-Mn Struc

tural Steel," Welding Journal, 55 (5), May

1976,Res.Suppl., pp. 135-s to 143-s.

2. Sawhil l,

J.

M., "Implant Tests of a Mn-

Mo-C b Steel and a Con ventiona l X65 Steel,"

Climax Molybdenum Report

L-176-111,

June 21, 1973, Ann Arbor, Michigan.

3. Looney, R. L., "Pipeline W el di ng -

Meeting Today's Quality Requirements,"

Lincoln Electric Technical Bulletin M642,

Jan. 1970.

4. Cooke, R. )., "An Evaluation of the

Thermal Cycles Imposed on the HAZ

During Manual Pipe Welding," Physical

Metallurgy Research Laboratories Internal

Report

PM-R-74-21,

CANMET, Dept. of

Energy, Mines and Resources, Ottawa,

Canada.

5.

Ito,

Y., and Bessyo, K., International

Institute of Welding Document No. 1X-

576-68.

WRC Bulletin 219

September 1976

Experimental Investigation of Limit Loads of Nozzles in Cylin

drical Vessels

by Fernand El lyin

Exper imental resul ts of e last ic-p last ic behavior and plast ic l imi t loads (y ie ld point loads) of f ive tee-

shaped cy l inder-cy l inder intersect ions and a p la in p ipe are repor ted herein. The intersect ing models were

machined f rom a s ingle hot - ro l led steel p late. The nozzle-vessel at tachments (or branch-pipe tee

connect ions) were subjected to one of the loading modes: in ternal pressure, in-p lane or out -of -p lane

couples appl ied to the nozzle ext remity . The out -of -p lane couple loading is found to be the cr i t ica l case.

Publ icat ion of th is repor t was sponsored by the Pressure Vessel Research Commit tee of the Welding

Research Counci l .

The pr ice of

WRC Bulletin 219

is $6.00 per copy. Orders should be sent wi th payment to the Welding

Research Counci l , Uni ted Engineer ing Center , 345 East 47th St reet , New York, NY 10017.

WRC Bulletin 221

November 1976

Analysis of Test Data on PVRC Specification No. 3, Ultrasonic

Examination of Forgings, Revision I and II

by R. A . Buchanan

The purpose of th is repo r t is to rev iew, analyze and draw conc lus ion s f rom data developed du r ing ef for ts

to test the val id i ty of the procedures a l lowed by PVRC Speci f icat ion No. 3, Revis ions I and I I . The a utho r

states that the only way to reduce the var iat ion in test data f rom one group to another would be to rest r ic t

the procedures of PVRC Speci f icat ion No. 3 so that only cer ta in equipment combinat ions or , i f pract ical ,

on ly one combina t ion cou ld be used .

Analysis of the Nondestructive Examination of PVRC Plate-

Weld Specimen 251JPart A

by

R

A. B u c h a n a n

Dur ing the fabr icat ion of PVRC plate-weld specimen 251J, 15 weld ing defects were del iberate ly

int roduced. Af ter fabr icat ion, the specimen was ul t rasonical ly examined for weld ing defects by a number of

d i f f e ren t company teams. The teams conduc ted the i r t es t s independent ly and had no knowledge o f t he

types or locat ions of the intent ional defects. Two di f ferent PVRC procedures for u l t rasonic examinat ion

were fo l lowed by the teams in their evaluat ion of the specimen.

Publ icat ion of these repor ts was sponsored by the Pressure Vessel Research Commit tee of the Welding

Research Counci l .

The pr ice of WRC Bulletin 221 in $7.00 per copy. Orders should be sent wi th payment to the Welding

Research Counci l , Uni ted Engineer ing Center . 345 East 47th St . , New York, NY 10017.

Documents

The Weldability of Some Arctic-Grade Line-Pipe Steels